A storage resource pool composed of a large amount of storage disks usually exists in a storage system. Physical logic storage units can be created on the storage resource pool. The physical logic storage units refer to logic storage units that are directly mapped to a physical storage space and the number of the physical logic storage units is usually restricted by the size of the actual available physical storage space. Besides, virtual logic storage units can be created based on the physical logic storage units for use by an upper-layer application. The virtual logic storage units are not restricted by the size of the physical storage space. A system administrator can create a large amount of virtual logic storage units, but space allocation is actually performed only when data is to be written. Therefore, the virtual logic storage units can easily implement different tiers to store various data to meet different user requirements.
A cache component usually also exists in the storage system and improves performance of data access by transparently storing the frequently accessed data in a faster storage medium (e.g., flash) relative to underlying storage disks. However, the cache is usually enabled and disabled based on the entire storage resource pool. In other words, in a plurality of virtual logic storage units based on the same storage resource pool, the cache function cannot be enabled for some more important virtual logic storage units and disabled for other less important virtual logic storage units.